The present invention relates to a semiconductor device comprising a control circuit and a power stage with a vertical current flow, integrated in monolithic form in a single chip.
The association on the same chip of a power stage realized with bipolar transistors (BJT) and the related control circuit, creates a very compact, efficient device, which has the following advantages over separate components:
the reliability and the efficiency of the device increases, as it is possible to insert a series of dedicated controls (e.g. "thermal shutdown", to switch-off the power stage when a certain maximum temperature is reached, "SOA" protection against direct secondary breakdowns, etc.), which, inasmuch as they are included on the same chip, are much more efficient than an external control; PA1 the cost of the system using a similar device is lower, as a single package is used instead of two (or more packages); this not only reduces the space and the weight of the system, but also increases overall reliability. PA1 a higher switching speed, and, as a result, lower power losses; PA1 a higher current density, and therefore reduced area of the device; PA1 a greater extension of the RBSOA area, and, as a result, reduced complexity of the driving circuit, as it is no longer necessary to protect the power stage while switching off inductive loads; PA1 an easier design of the power stage, on account of the modular structure of the BMFET transistor (in fact, since the BMFET transistor is made up of a plurality of identical elementary cells, a certain operating current is ensured simply by parallel connecting the required number of elementary cells).
On the other hand the use of BJT-type power stages makes it more difficult to solve other problems, such as, basically, the low switching speed, the maximum current density, the extension of the Reverse Bias Safe Operating Area (RBSOA). It is however a known fact that the use of power stages of the MOS type is only advisable for devices which can operate at low voltages, due to the problems connected to excessive series drain resistance (Ron).